The subject matter herein relates generally to radioisotope production systems and, more specifically, to controlling beam properties of a particle beam during radioisotope production.
Radioisotopes (also called radionuclides) have several applications in medical therapy, imaging, and research, as well as other applications that are not medically related. Systems that produce radioisotopes typically include a particle accelerator, such as a cyclotron, that accelerates a beam of charged particles. The charged particles may be H-ions, although positive ions may also be used. The system directs the particle beam such that the charged particles collide with a target material to generate the radioisotopes. The cyclotron includes an ion source that provides ions into an acceleration chamber of the cyclotron. The cyclotron uses an electrical field and a magnetic field (or flux) to accelerate and guide the charged particles along an orbit within the acceleration chamber. The magnetic field may be generated by an electromagnet and a magnet yoke that surrounds the acceleration chamber. A majority of the orbit of the particle beam typically exists between two poles of the magnet yoke.
The electrical fields are generated by one or more radio frequency (RF) electrodes (or dees) that are located within the acceleration chamber. The RF electrodes are electrically coupled to an RF power generator that energizes the RF electrodes to provide the electrical field. The electrical and magnetic fields cause the charged particles to take a spiral-like orbit that has an increasing radius. When the charged particles reach an outer portion of the orbit, the charged particles are directed toward the target material for isotope production.
The electromagnet is controlled by a drive current. During operation of the cyclotron, the magnetic field generated by the electromagnet and the magnetic yoke is weakened as the magnetic material (e.g., steel in the magnetic yoke) is heated. Conventional systems may increase the drive current in accordance with a predetermined algorithm to maintain a suitable magnetic field for controlling the particle beam. The algorithm may be based on historical data from prior sessions. For example, the algorithm may require that the drive current be increased by a fixed amount after ten minutes of operation (or other predetermined time). Although these algorithms can be effective, the isotope production of the conventional system may become less efficient as the session continues.